[kermit80]

I think it was something stuck in your radiator.  If it was your thermostat....it may be your thermostat...but usually your thermostat would stay stuck...and your temp would stay HOT....it would reject waterflow...the radiator cap is good to change if you have had it for a long time...because it could seep air into the system which causes your coolant to lose pressure and boil faster..anytime you have a leak in the system..your boiling point of the coolant goes down allot....you could try getting away with just changing the cap..and looking for any other leaks.  I just had a really small one recently on the upper hose.  If you want to not deal with it anymore...change the thermostat as well.....and first take it out...put the hose back on..and flush the system.....do that several times..before you put in the new thermostat.  Check the hoses if they are weak and easy to push in....cracked or bulging.....replace those hoses so you don't deal with them later.  Then you should be set!!!  I still gotta change my thermostat and flush the system...that will work wonders....